The present invention relates to rotary machines, including rotary engines, rotary motors, and compressors.
The advent of rotary engines was intended to supplant reciprocating engines, thereby to reduce energy losses caused by the reciprocation of pistons, to reduce the number of moving parts, and also, friction losses. In this way it was intended to increase the number of revolutions per minute, and also to increase engine efficiency.
Rotary engines may include a pair of rotors arranged for rotation within a sealed engine cavity. The rotors are connected to an output shaft or driver. A combustible fuel mixture is provided to the engine cavity and ignited. An increase in pressure in the engine cavity due to ignition of the fuel-air mixture results in a driving force being applied to the rotors, thereby causing rotation of the driver.
There are also known rotary pumps and motors which have certain similarities to the above-described engine. An indication of the state of the art may be obtained by referring to the following patent publications:
U.S. Pat. No. 3,078,807, entitled Dual-Action Displacement Pump;
French Patent No. 9204757, publication No. 2,690,201;
U.S. Pat. No. 3,726,617, entitled Pump or a Motor Employing a Couple of Rotors in the Shape of Cylinders with an Approximately Cyclic Section; and
U.S. Pat. No. 5,152,683, entitled Double Rotary Piston Positive Displacement Pump with Variable Offset Transmission Means.
The above patents generally do not provide structures which are conducive for use as internal combustion engines.
In the field of internal combustion engines, it is desirable to sustain high operating temperatures, thereby to maximize engine efficiency, in accordance with the well-known Carnot Law.
In the field of rotary internal combustion engines, there are known the following publications: U.S. Pat. No. 2,845,909, entitled Rotary Piston Engine, to Pitkanen; and U.S. Pat. No. 4,666,383, entitled Rotary Machine, to Mendler.
Pitkanen teaches a rotary piston engine having a pair of cam-shaped rotors which are arranged for parallel rotation inside an engine casing. Pitkanen is unable to work at high speeds due to the shape of the rotors, and, furthermore, seeks to cool the engine, thereby preventing an increase in temperature which, in Pitkanen""s engine, is undesired. This results in an inefficient engine, based on the well-known Carnot Law, in which efficiency is proportional to the temperature difference between the interior and exterior of the engine, which Pitkanen does not sustain.
Mendler teaches a rotary piston engine having a pair of cam-shaped rotors which are arranged for parallel rotation inside an engine casing. Each rotor is described in the cited patent (column 8, lines 1-6) as having xe2x80x9cmajor and minor cylindrical surfaces . . . , each centered on the axis A of the rotor, and diametrically opposed, . . . joined by cylindrical transition surfaces . . . xe2x80x9d Furthermore, a plurality of seals are provided, thereby to provide rotor-to-rotor and rotor-to-bore-wall seals (column 7, lines 62-64). It will be appreciated that, due to the presence of seals, the engine taught by Mendler is not only unable to sustain high rotational speeds, due to friction losses, but also cannot operate at high temperatures, due to the necessary presence of lubricating oil in the engine cavity.
The term xe2x80x9cnon-touching sealxe2x80x9d is used to mean a non-physical barrier in a dynamic situation in which a working fluid is confined between a plurality of surfaces for a specified period of time, wherein at least one of the surfaces is in motion relative to the other and is spaced apart therefrom across a gap of predetermined dimensions, and wherein the dimensions of the gap and the relative velocity therebetween combine so as to prevent significant leakage of working fluid therepast, during the specified period of time. This is in contradistinction to dynamic seals which rely, solely or partially, on the presence of an additional sealing element to be in touching contact with a surface past which it is sought to prevent leakage of a working fluid.
The present invention seeks to provide a rotary machine which embodies yet further improvements in rotary machine operation, beyond those claimed and described in applicant""s co-pending application U.S. Ser. No. 09/099,521 entitled Rotary Machine, the contents of which are incorporated herein, by reference.
In particular, the present invention seeks to provide a rotary machine which is characterized by a non-cylindrical rotor construction which facilitates the attainment of an elevated compression ratio, together with an attendant increase in fuel efficiency.
Additional advantages will become apparent from the following description.
There is thus provided, in accordance with a preferred embodiment of the invention, an improved rotary machine which includes:
a housing having formed therein a generally elongate cavity, the cavity being formed by a pair of adjoining, partially overlapping cylindrical bores, each bore being separated from an adjoining bore by a pair of non-joining partition walls;
a pair of non-cylindrical rotors arranged in the pair of adjoining bores, each rotor having a curved outer surface formed of a plurality of contiguous mutually tangential curved portions, wherein each rotor is disposed in one of the bores for synchronized, non-touching and same-directional rotation with the other of the pair of rotors;
a pair of rotor shafts associated with each pair of rotors, each rotor shaft extending through one of the bores, and mounted transversely to each rotor so as to provide eccentric rotation thereof in the bore;
a gear assembly and a driver associated with the rotor shafts, the assembly and the driver, cooperating to provide synchronized same directional rotation of the rotor shafts; and
a plurality of gas ports formed in the housing and communicating with the elongate cavity thereof, for permitting selectable intake and exhaust of working gases,
wherein, introduction of a working gas into interactive association with the rotors causes rotation of the pair of rotors and thus also of the driver.
Additionally in accordance with a preferred embodiment of the invention, each bore has a geometric center, and each rotor is mounted for rotation about a rotation axis spaced from the geometric center by a predetermined eccentricity;
each cavity is bounded by a pair of parallel wall surfaces transverse to the rotation axis;
the plurality of gas ports includes at least a pair of gas ports provided in communication with each bore, wherein a first of the gas ports is arranged at a first radius from the geometric center and a second of the gas ports is arranged at a second radius from the geometric center, wherein the second radius has a magnitude smaller than that of the first radius; and
wherein each rotor is operative to rotate within one of the bores so as to periodically uncover the first port, thereby to enable a flow therethrough of a working gas.
Additionally, in accordance with a preferred embodiment of the invention, the pair of rotors are disposed in substantially equal angular orientation relative to the rotation axes thereof.
Additionally, in accordance with a preferred embodiment of the invention, each rotor has a pair of flat, parallel surfaces disposed in dynamic, non-touching, sealing relation with the pair of parallel wall surfaces of each cavity, and each rotor has formed therein a throughflow portion which is formed so as to be brought periodically into communicative association with the interior of the cavity and with the second gas port, so as to facilitate gas communication therebetween.
Additionally, in accordance with a preferred embodiment of the invention, each pair of rotors includes first and second rotors arranged for rotation within a predetermined pair of adjoining, respective, first and second bores such that the outer surfaces of the first and second rotors are always in dynamic, non-touching, sealing relation with each other.
Additionally, in accordance with a preferred embodiment of the invention, the machine is an internal combustion engine, and the rotors are operative, during the rotation thereof, to cooperate with the partition walls and predetermined portions of the side walls so as to periodically form combustion chambers therewith, and wherein the housing and the rotors are formed of a substantially non-heat conducting material, thereby to enable an elevated temperature to be sustained within the combustion chambers during operation of the engine.
Additionally, in accordance with a preferred embodiment of the invention, the elevated temperature, once attained during operation of the engine, is sufficient to cause combustion of an air-fuel mixture in the combustion chambers, even in the absence of an air compression ratio of greater than 1:19.
Additionally, in accordance with a preferred embodiment of the invention, the substantially non-heat conducting material is a ceramic material.
Additionally in accordance with a preferred embodiment of the invention, the first port is a working gas intake port, and the second port is a working gas exhaust port, and wherein each pair of rotors are operative to rotate through a working cycle having first and second portions,
wherein, during the first portion of the working cycle,
the first and second rotors are operative to rotate into first positions whereat they are initially spaced from a first side of the cavity so as to define a first working space therewith, and the first rotor is operative to uncover the working gas intake port in the first bore thereby to admit air into the space;
the first rotors and second rotors are operative to rotate into second positions so as to reduce the volume of the first working space and thus compress the working gas therein; and
the first rotors and second rotors are operative to be rotated into third positions in response to an expansion of the working gas in the first working space, and such that the second rotor is operative to bring the throughflow portion thereof into communicative association with the interior of the cavity and with the exhaust port in the second bore, so as to facilitate exhausting of working gas from the second working space.
and wherein, during the second portion of the working cycle,
the first and second rotors are operative to rotate into fourth positions whereat they are initially spaced from a second side of the cavity, opposite the first side of the cavity, so as to define a second working space therewith, and the second rotor is operative to uncover the working gas intake port in the second bore thereby to admit air into the second working space;
the first rotors and second rotors are operative to rotate into fifth positions so as to reduce the volume of the second working space and thus compress the working gas therein; and
the first rotors and second rotors are operative to rotate into sixth positions so as to permit expansion of the working gas in the second working space, and such that the first rotor is operative to bring the throughflow portion thereof into communicative association with the interior of the cavity and with the exhaust port in the first bore, so as to facilitate exhausting of working gas from the second working space.
Additionally, in accordance with a preferred embodiment of the invention, during the first portion of the working cycle, as the first rotors and second rotors rotate into the third positions, the first rotor is operative to uncover the intake port in the first bore, thereby to permit a throughflow between the intake port in the first bore, the first working space, the throughflow portion of the second rotor, and the exhaust port in the second bore;
and wherein, during the second portion of the working cycle, as the first rotors and second rotors rotate into the sixth positions, the second rotor is operative to uncover the intake port in the second bore, thereby to permit a throughflow between the intake port in the second bore, the second working space, the throughflow portion of the first rotor, and the exhaust port in the first bore.
Additionally, in accordance with a preferred embodiment of the invention, the machine is an internal combustion engine, the first and second working spaces are first and second combustion chambers, the working gas intake ports are air intake ports, and the working gas exhaust ports are combustion gas exhaust ports,
and wherein the machine also includes at least first and second fuel injectors for injecting fuel into the first and second combustion chambers so as to provide fuel-air mixtures therein and so also as to enable combustion of the fuel-air mixtures, thereby to provide a rotational force on the second rotor during the first portion of the working cycle, and on the first rotor during the second portion of the working cycle.
Additionally, in accordance with a preferred embodiment of the invention, the machine also includes ignition apparatus associated with the first and second combustion chambers, for selectably igniting the fuel-air mixtures therein.
Additionally, in accordance with a preferred embodiment of the invention, the machine is a motor, associable with an external source of pressurized working gas, wherein each bore has a geometric center, and each rotor is mounted for rotation about a rotation axis spaced from the geometric center by a predetermined eccentricity;
each cavity is bounded by a pair of parallel wall surfaces transverse to the rotation axis;
the plurality of gas ports includes at least a pair of gas ports provided in each bore, wherein a first of the gas ports is arranged at a first radius from the geometric center and a second of the gas ports is arranged at a second radius from the geometric center, wherein the second radius has a magnitude larger than that of the first radius; and
wherein each rotor is operative to rotate within one of the bores so as to periodically uncover the second port, thereby to enable a flow therethrough of a working gas.
Additionally, in accordance with a preferred embodiment of the invention, each rotor has a pair of flat, parallel surfaces disposed in dynamic, non-touching, sealing relation with the pair of parallel wall surfaces of each cavity, and each rotor has formed therein a throughflow portion which is formed so as to be brought periodically into communicative association with the interior of the cavity and with the first gas port, so as to facilitate gas communication therebetween.
Additionally, in accordance with a preferred embodiment of the invention, each pair of rotors includes first and second rotors, each arranged for rotation within a predetermined pair of adjoining, respective, first and second bores such that the outer surfaces of the first and second rotors are always in dynamic, non-touching, sealing relation with each other.
Additionally, in accordance with a preferred embodiment of the invention, the first port is a pressurized working gas intake port, and the second port is a working gas exhaust port.
Additionally, in accordance with a preferred embodiment of the invention, the machine is a compressor, associable with an external source of working gas, wherein each bore has a geometric center, and each rotor is mounted for rotation about a rotation axis spaced from the geometric center by a predetermined eccentricity;
each cavity is bounded by a pair of parallel wall surfaces transverse to the rotation axis;
the plurality of gas ports includes at least a pair of gas ports provided in each bore, wherein a first of the gas ports is arranged at a first radius from the geometric center and a second of the gas ports is arranged at a second radius from the geometric center, wherein the second radius has a magnitude larger than that of the first radius; and
wherein each rotor is operative to rotate within one of the bores so as to periodically uncover the second port, thereby to enable a flow therethrough of a working gas.
Additionally, in accordance with a preferred embodiment of the invention, each rotor has a pair of flat, parallel surfaces disposed in dynamic, non-touching, sealing relation with the pair of parallel wall surfaces of each cavity, and each rotor has formed therein a throughflow portion which is formed so as to be brought periodically into communicative association with the interior of the cavity and with the first gas port, so as to facilitate gas communication therebetween.
Additionally, in accordance with a preferred embodiment of the invention, each pair of rotors includes first and second rotors, each arranged for rotation within a predetermined pair of adjoining, respective, first and second bores such that the outer surfaces of the first and second rotors are always in dynamic, non-touching, sealing relation with each other.
Additionally, in accordance with a preferred embodiment of the invention, the second port is a working gas intake port, and the first port is a pressurized working gas exhaust port.
There is also provided, in accordance with an alternative preferred embodiment of the invention, for use with a rotary machine, a rotor which includes:
a pair of parallel side surfaces; and
a curved outer surface formed between the pair of parallel side surfaces, formed of a plurality of contiguous mutually tangential curved portions.
Additionally, in accordance with a preferred embodiment of the invention, the curved outer surface includes:
a major portion defining a first major arc subtending a predetermined angle at a predetermined center of rotation, and having a first radius;
a minor portion defining a first minor arc subtending a predetermined angle at the predetermined center of rotation, and having a second radius, shorter than the first radius, the major and minor arcs being arranged along an axis of symmetry; and
a pair of similar, intervening curved portions extending tangentially between major and minor arcs.
Additionally, in accordance with a preferred embodiment of the invention, each of the pair of intervening curves is formed of mutually tangential, a second major arc and a second minor arc, of predetermined radii.